Field of the Invention
The present invention relates to a method for performing an operation related to a Radio Link Failure (RLF) in wireless communication systems, and more particularly, to a method for performing an operation related to the Radio Link Failure for a specific service of low latency/high reliability and an apparatus for supporting the same.
Discussion of the Related Art
Recently, the importance of the 5G mobile communication technology has been increased more and more. And one of the actualized fields is a Reliable Communication.
The Reliable Communication means a new communication service that is realized through the Error Free Transmission or Service Availability for the realization of a Mission Critical Service (MCS).
The necessity of the Reliable Communication has been recognized since it is a part of Machine-Type Communication that satisfies Real-Time requirements for the Traffic Safety, the Traffic Efficiency, the E-Health, the Efficient Industrial Communication, and so on.
In addition, a Reliable Connection should be provided to the Reliable Communication for the applications of delay-sensitive such as the Traffic Safety or the Mission Critical Machine-Type Communications (MTCs) of a special purpose.
Furthermore, the necessity of the Reliable Communication has been also recognized for the purpose of a Medical/Emergency Response, a Remote Control, a Sensing, and the like.
It is anticipated that significant increases are required in the End-to-End Latency, the Ubiquity, the Security, the Availability/Reliability, and the like for the MCSs in comparison with the conventional UMTS/LTE and LTE-A/Wi-Fi.
That is, the commercialized wireless technologies (including 3GPP LTE and LTE-A) proposed up to now fail to guarantee the adequate performance for providing various MCSs in the aspect of the Real-Time requirements and the Reliability requirements.
In addition, as the scenarios that are applicable to the 5G mobile communication environment for the MCSs, the following services may be exemplified.                Control a robot arm remotely in order to realize the Industrial Automation, or transport heavy and large goods through the remote control for Automated Guided Vehicles (AGVs)        Remotely control a drone in order to provide the physical distribution, the remote healthcare service, and other various public services        Safely exchange the information required between vehicles in order to provide an autonomous vehicle service or safely deliver the safety signal that notifies a hidden vehicle that is not detected by a vehicle sensor (e.g., camera, radar, etc.) or a forward collision        
In the case that the radio link (serving link) quality of a serving base station is degraded to an extent of not proper for MCSs although another available alternative base station link is determined, the above-mentioned services should be provided continuously.
Accordingly, in the case that the degradation of the radio link quality of a serving base station is detected and it is determined that the radio link quality of the serving base station is not proper for providing MCSs, a method is required for activating another multilink quickly and for configuring an MCS bearer through the activated multilink.
Owing to the reasons, in order for the Reliable Communication of 5G to be available, a terminal utilizes all radio links around and gives instruction so as to maximize the radio link according to situations, and therefore, the decrease of radio link outage for providing MCS should be considered as an essential element.
In order to fulfill these requirements, when the quality of radio link of the serving base station is degraded, a terminal may determine an optimal alternative base station among the alternative base stations which are already secured, and configure a bearer quickly through an RRC connection activation to the corresponding alternative base station and the radio link of the corresponding alternative base station.
However, the current LTE/LTE-A system is designed to process the recovery from the Radio Link Failure (RLF) very conservatively.
Owing to this, it may be difficult to search other alternative available base stations quickly according to the channel situation of UE, and to secure alternative available base station for the activation of connection to the corresponding alternative base stations.
That is, during the link switching procedure of a terminal from the radio link of a serving base station to the radio link of an alternative base station, the RLF may occur since the reception signal strength from the serving base station (or serving cell) is not maintained adequately until the successful completion of the wireless access to the radio link of the alternative base station.
Accordingly, the RLF avoiding method is required for minimizing the continuity damage in providing a specific service (e.g., MCS) that satisfies the requirements of 5G through the alternative base stations which are already secured.